From: Jan Beulich <jbeulich@suse.com>
To: Hongyan Xia <hx242@xen.org>
Cc: xen-devel@lists.xenproject.org, julien@xen.org
Subject: Re: [PATCH v6 09/15] efi: use new page table APIs in copy_mapping
Date: Thu, 30 Apr 2020 14:42:40 +0200 [thread overview]
Message-ID: <6f2447ba-e12a-9241-6c2c-a7a49059c09b@suse.com> (raw)
In-Reply-To: <6c27c79964eb16eba4743515689b9fd7eb3409d1.1587735799.git.hongyxia@amazon.com>
On 24.04.2020 16:09, Hongyan Xia wrote:
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -1454,16 +1454,20 @@ static __init void copy_mapping(unsigned long mfn, unsigned long end,
> continue;
> if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
> {
> - l3dst = alloc_xen_pagetable();
> - BUG_ON(!l3dst);
> + mfn_t l3mfn = alloc_xen_pagetable_new();
> +
> + BUG_ON(mfn_eq(l3mfn, INVALID_MFN));
> + l3dst = map_domain_page(l3mfn);
> clear_page(l3dst);
> efi_l4_pgtable[l4_table_offset(mfn << PAGE_SHIFT)] =
> - l4e_from_paddr(virt_to_maddr(l3dst), __PAGE_HYPERVISOR);
> + l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR);
> }
> else
> - l3dst = l4e_to_l3e(l4e);
> - l3src = l4e_to_l3e(idle_pg_table[l4_table_offset(va)]);
> + l3dst = map_l3t_from_l4e(l4e);
> + l3src = map_l3t_from_l4e(idle_pg_table[l4_table_offset(va)]);
> l3dst[l3_table_offset(mfn << PAGE_SHIFT)] = l3src[l3_table_offset(va)];
> + unmap_domain_page(l3src);
> + unmap_domain_page(l3dst);
> }
> }
This looks very inefficient - you establish and tear down two mappings
per loop iteration, when really you may end up copying all 512 slots
between the same pair of L3 tables.
Jan
next prev parent reply other threads:[~2020-04-30 12:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-24 14:08 [PATCH v6 00/15] switch to domheap for Xen page tables Hongyan Xia
2020-04-24 14:08 ` [PATCH v6 01/15] x86/mm: map_pages_to_xen would better have one exit path Hongyan Xia
2020-04-24 14:08 ` [PATCH v6 02/15] x86/mm: make sure there is one exit path for modify_xen_mappings Hongyan Xia
2020-04-24 14:08 ` [PATCH v6 03/15] x86/mm: rewrite virt_to_xen_l*e Hongyan Xia
2020-05-20 9:27 ` Jan Beulich
2020-04-24 14:08 ` [PATCH v6 04/15] x86/mm: switch to new APIs in map_pages_to_xen Hongyan Xia
2020-04-24 14:08 ` [PATCH v6 05/15] x86/mm: switch to new APIs in modify_xen_mappings Hongyan Xia
2020-04-24 14:08 ` [PATCH v6 06/15] x86_64/mm: introduce pl2e in paging_init Hongyan Xia
2020-05-20 9:35 ` Jan Beulich
2020-04-24 14:08 ` [PATCH v6 07/15] x86_64/mm: switch to new APIs " Hongyan Xia
2020-05-20 9:46 ` Jan Beulich
2020-05-27 15:01 ` Hongyan Xia
2020-04-24 14:08 ` [PATCH v6 08/15] x86_64/mm: switch to new APIs in setup_m2p_table Hongyan Xia
2020-05-20 9:54 ` Jan Beulich
2020-04-24 14:09 ` [PATCH v6 09/15] efi: use new page table APIs in copy_mapping Hongyan Xia
2020-04-30 12:42 ` Jan Beulich [this message]
2020-04-24 14:09 ` [PATCH v6 10/15] efi: switch to new APIs in EFI code Hongyan Xia
2020-04-30 12:55 ` Jan Beulich
2020-04-24 14:09 ` [PATCH v6 11/15] x86/smpboot: clone_mapping should have one exit path Hongyan Xia
2020-04-30 14:59 ` Jan Beulich
2020-04-24 14:09 ` [PATCH v6 12/15] x86/smpboot: switch pl*e to use new APIs in clone_mapping Hongyan Xia
2020-04-30 15:15 ` Jan Beulich
2020-05-11 10:55 ` Hongyan Xia
2020-04-24 14:09 ` [PATCH v6 13/15] x86/mm: drop old page table APIs Hongyan Xia
2020-05-20 10:09 ` Jan Beulich
2020-05-27 15:19 ` Hongyan Xia
2020-04-24 14:09 ` [PATCH v6 14/15] x86: switch to use domheap page for page tables Hongyan Xia
2020-04-24 14:09 ` [PATCH v6 15/15] x86/mm: drop _new suffix for page table APIs Hongyan Xia
2020-05-20 9:56 ` Jan Beulich
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